1. Need For and Benefits of Tier 3 Vehicle and Fuel Standards

3. The Air Pollution Problem Remains Very Serious With Millions Breathing Unhealthy Air

4. Vehicles Remain A Major Source
This is especially true with regard to NOx and VOCs
the precursors of ozone.

7. Technology Exists To Substantially Reduce Emissions Further
Potential Tier 3 Technologies are almost entirely the same as those already on California PZEV/SULEV (i.e., EPA Tier 2 bin 2) models of today
increased precious metal (Pt/Pd/Rh) catalyst loading
optimized close-coupled catalyst
secondary air injection pump
evaporative control system
active HC adsorber on limited models
Estimated Cost ~ $150

8. Low Sulfur Gasoline is Key
All Existing Catalyst Equipped Vehicles Will Be Improved
With Lower Sulfur Gasoline
Poisoning of Precious Metal
HC, CO, NOx
SO2
Precious Metal
Poisoning of Washcoat
Lower O2 Storage Ability
This shows how sulfur deteriorates the catalyst performance.
Basically two paths are estimated as the reason why sulfur affects exhaust emissions.
First sulfur in fuel changes to SO2 through combustion process. SO2 is adsorbed on the surface of precious metals and obstructs purification of exhaust gas.
SO2 in exhaust gas is oxidized by the precious metals, ans is stored as SO4 reacting with cerium and alumina. As a result, oxygen storage ability of these materials is spoiled.
Cerium
SO2
SO3 O2
CeO2 ⇒ Ce（SO4)2 O2
Alumina
Precious Metal
Al2O3 ⇒ Al2（SO4)3

10. Naphtha Hydrotreating (“Post-treating”) To Reduce The Sulfur Content
Fluidized Catalytically Cracked (FCC) Naphtha Is The Primary Source Of Sulfur In The Gasoline
Naphtha Hydrotreating (“Post-treating”) To Reduce The Sulfur Content
All existing FCC post-treaters would require revamping to meet the 10-ppm sulfur standard;
The average capital expenditure for revamping is 30 percent of the expenditure for new post-treaters (even though some of the existing units may require no revamping); and
The target rate of return on refinery investments is 7 percent before tax.
Cost ~ $0.008/ gallon

11. Cost Per Ton of NOx Reduced
Cost Effectiveness of Tier 3 Low-Sulfur Gasoline Relative to Other NOx Reduction Measures
NOx Reduction Measure
Cost Per Ton of NOx Reduced
Tier 3 Low-Sulfur Gasoline
$3,300
Oil/Gas Boilers Serving EGUs
$1, ,700
New Small Gas Boilers
$3, ,000
Municipal Waste Incinerators
$2,140 (SNCR)
HEDD EGUs
$45,000 - $300,000
per unit
Stationary Generators
$39, ,700
Minor New Source Review
$600 - $18,000
Source: Senate Staff Briefing on the Need for Strong NOx Caps in the Eastern U.S – OTC, ICAC, NACAA and Maryland (July 2010).